The Ultimate Tarantula Humidity Guide

Tarantula Humidity GuideA quick Google search about tarantula care and you will see that humidity plays a vital role in keeping your T healthy. Of course, as with most things, there is some disagreement regarding the importance of humidity, and some hobbyists will say it’s unnecessary.

Is humidity important to tarantulas? Yes. Dehydration is the foremost killer of tarantulas, but by keeping the enclosure they live in humid, it will contribute to their overall hydration levels. Humidity also makes the process of molting easier for tarantulas.

Getting the humidity just right sometimes be a difficult task; your Ts enclosure either stays too dry or turns into a soggy mess. To help you find a balance, read on for some tips and tricks.

Why is Humidity Important?

As briefly mentioned above, dehydration is a killer, and we as T owners must do what we can to keep our pets hydrated.

Tarantulas lose water in the following ways:

  • Through their leg joints where the epicuticle is thin.
  • Through the inner surface of their book lungs.
  • During a molt. Water acts as a lubricant between the old exoskeleton and the new one. It also dissolves important enzymes during this process.
  • While eating. Yes, although most of their water needs are met through their food, the act of breaking down the food by the secretion of fluids and the fluid in the discarded food bolus does dehydrate them some.
  • During defecation.
  • When laying eggs.
  • While spinning silk.

As you can see, there are quite a few ways your T can lose water and become dehydrated; making it essential to ensure the humidity levels are high enough.

Apart from the general hydrating effects of high humidity, there’s also the added benefit of it lessen your Ts chances of getting stuck in its old exoskeleton during the molting process.

When your tarantula sheds its old skin, fluid gets pushed into its cephalothorax (upper body) by abdominal contractions, increasing the pressure on the stretched exoskeleton.

This added force will make it easier for your tarantula to break through its old skin in areas where there are weak spots.

However, should your tarantula be dehydrated because it does not have access to water or its living conditions are too dry, then there is too little fluid in between the old and new exoskeletons to act as a lubricant. This will make it very difficult for your tarantula to shed its old skin.

Another reason why humidity is important is that it helps your tarantula breathe. Tarantulas have book lungs; it’s called this because it looks like the pages of a book.

Oxygen passes through these sections, but the surface of the lungs needs to be moist for the oxygen to be absorbed effectively. If your T’s enclosure is too dry, it is going to have a negative effect on its ability to breathe.

Okay, so you read that, and now you think the higher the humidity, the better, right? Wrong. Tarantulas don’t do well in soggy conditions, and it will cause them physiological stress.

A mushy environment is also the perfect breeding ground for unwanted visitors such as mold, mites, fungus, and bacteria.

We’re basically looking for a perfect balance.

What humidity do tarantulas need?
Lasiodora parahybana

What is Good Humidity?

This is a trick question. You should know by now that your tarantula’s enclosure should be based on its species. Tarantulas are a diverse group of spiders (btw, did you know that there are many differences between normal spiders and tarantulas? We show you 12 differences here!) that live anywhere from dry savannah areas and deserts to moist tropical jungles.

So, as you can imagine, this is not a one habitat fits all situation.

It’s best to do some thorough research about the tarantula you plan on getting so that you can match its environment as closely as possible to that which it would live in in the wild.

That being said, sometimes you won’t be able to find the appropriate information, especially if you’re moving past beginner-type tarantulas.

As a general guideline, a healthy humidity for Ts is anywhere from 75-85%, and the substrate should be slightly moist but not dripping wet.

Of course, you should strike a balance between humidity and heat. You can read our heating guide to help you find the perfect balance between the two. 

What is Bad Humidity?

Bad humidity can be either too dry or too wet. Keeping your spider in bone-dry conditions or in an environment that is closer to a swamp than a jungle, you’re asking for trouble.

The humidity should never drop lower than 50%. If you find your tarantula spending a lot of time hovering over its water dish, it’s a sign that the environment is too dry, and the T is trying to moisten its book lungs.

Always consider where your tarantula comes from; is it a rainforest species, or does it come from a dry African savannah? Use this information to adjust the humidity to your Tarantula’s needs.

How Do you Measure Humidity Properly?

There are a few ways you can measure the moisture levels in your tarantula’s enclosure.

The first is by using a hygrometer; basically, a thermometer that measures moisture and not temperature. You get low-cost dial versions and then more expensive digital types.

Digital hygrometers seem to be slightly more accurate than dial-based ones, so I recommend saving up a little extra and getting yourself a good quality digital hygrometer. We recommend getting this digital hygrometer here!

Another way of monitoring the moisture in your Ts enclosure is by eyeballing it. If you see a small amount of condensation on the glass, that is a good thing, and it means the humidity is adequate.

However, if there’s a mini waterfall running down the sides of the enclosure, it’s too wet, and you will need to let things dry out a bit.

You can also look at the substrate to gauge the humidity levels; slightly moist substrate is perfect, but if visible pools of water are forming in areas, it is too moist.

You can check out our article about the best substrate to use for your T’s enclosure. This can help you determine how much wetness you can add to your substrate.

It’s a good idea to spray your tarantula’s enclosure once or twice a week and then allow it to dry out in between. In nature, humidity isn’t constant, so taking this approach won’t be harmful to your T, and it has the added benefit of preventing fungi from forming.

How To Increase Humidity

Increasing the humidity is much easier than removing excess moisture, so be careful when attempting to boost humidity that you don’t go overboard.

You can try the following to get the humidity to rise:

1. Overfill a water dish to wet the substrate.

Since increasing humidity levels boils down to adding more water, this is an ideal way to get things a little wetter. But, no heavy hands! You want to add water in a controlled manner and not turn your T’s home into a swimming pool.

The substrate will absorb the water, and it will be released slowly as the water warms up.

How to increase humidity in a tarantula tank?
Poecilotheria rufilata

2. Mist the enclosure.

Some tarantula hobbyists swear by misting while others say it makes no difference. My view: it can’t hurt. The only important thing to note is that you use a mister bought specifically for this purpose; you don’t want to introduce harmful chemicals into your T’s enclosure.

The water should be at room temperature, or if it is an emergency and you need to increase the humidity stat, you can use lukewarm water as this evaporates quicker and raises the humidity immediately.

Don’t spray directly onto your tarantula. You may think this will help with any dehydration, but all it will do is cause unnecessary stress. Be kind to your T.

3. Move water bowl to the warm area of the enclosure.

If you use a heating pad (another hot-button issue in the world of owning pet tarantulas), you can move the water dish to the warm side of the enclosure. This way, water will evaporate quickly, and there will be more moisture in the air.

Just make sure to check the levels of the water bowl regularly if you employ this method. You may have to fill the dish more than usual. Keeping the water dish full at all times will also keep the humidity up as the water will slowly evaporate over time.

4. Restrict ventilation

The more ventilation holes in the enclosure, the quicker it will dry out. You want to create a ‘micro-climate’ inside your T’s enclosure and to do this, there should be just enough cross ventilation and airflow to not allow the environment from becoming too dry.

Of course, you don’t want to restrict airflow too much as that will create a stuffy and dangerous environment for your tarantula.

5. Give your tarantula enough space to burrow

I know, you want to see your tarantula so only offer it a shallow depth of substrate to reduce any burrowing.

That’s totally up to you but just know that burrowing gives your tarantula the opportunity to hide if the moisture in the air is too much, to dig towards areas of the substrate that are wetter and hence offer more humidity.

Even species that don’t dig will enjoy the extra depth because the bottom levels of the substrate will remain moist as the top dries and this trapped moisture will slowly release with time, increasing humidity.

6. Use a humidifier

If you tend to use a furnace, chimney or wood stove a lot, the humidity levels in your tarantula’s enclosure can get dangerously low. And, since the above steps may not be enough to get the humidity levels high enough, you may want to consider buying a humidifier.

This will easily raise the moisture in the air.

  • Tip: Keep part of the enclosure a bit drier. That way, your tarantula can choose between walking on dry or wet substrate based on its needs.

How To Decrease Humidity

Oh dear, depending on how bad of a swamp you created, things may get very messy.

If it is a case of too much condensation on the sides of the glass or the substrate got too wet in a specific part of the enclosure, no worries; don’t add any more water and just let it dry out with time.

You can also increase ventilation to help the excess water vapor escape; open any closed vents or cut extra holes for airflow.

Righto, that’s the easy scenario but what if somehow the whole enclosure is a wet mess and puddles are forming everywhere? Well, it’s time to employ extreme measures – you have to start afresh.

Take your T and place it in a temporary home (don’t forget to add a water dish). Now you can remove the soaked substrate. Thoroughly clean the cage and any décor and then allow it to dry out.

Once dry, start rebuilding your tarantula’s home. You may want to consider using a substrate that absorbs excess moisture better; coir fiber, for example, is good at sucking up extra wetness.

After you’re done, and you have placed your tarantula back in its enclosure, you have to take everything you have read up to this point and apply it to make sure that you maintain and control the moisture more carefully to avoid this from happening again.How to decrease humidity in a tarantula tank?

Arguments Against Humidity

Tarantula hobbyists don’t always agree on everything and humidity is one of the issues that have been debated for years and will continue to be for years to come.

They mostly argue that most tarantula species do well in enclosures with enough cross ventilation and containing a water dish – that’s all they need.

Here are some reasons why some tarantula owners believe this whole humidity issue is totally overrated.

Tarantulas are not so fragile

Ts are very adaptable. They MUST be if you take into account the fact that they have survived millions of years of evolution and climate change. So, will a lower than ideal level of humidity really do them much harm?

Yes, there are some species that require very humid conditions that will likely kill other species, but in between these extremes, you will find a large margin for error when it comes to setting up your T’s enclosure.

Tarantulas spend most of their time in burrows

Many species of tarantula dig themselves deep into the earth. The temperature and humidity inside these burrows are much different than outside.

This suggests that we can’t actually know what the ideal humidity levels are for many of these species since we’re yet to measure inside a burrow in the wild. Knowing this, some tarantula hobbyists believe that the humidity requirements found on care sheets are basically useless.

They feel stressing over matching these numbers is completely unnecessary.

Tarantulas carry around enough water

Ts are pretty big compared to other terrestrial invertebrates, and a lot of that is water. That makes tarantulas walking water banks and mean they have access to this water should they get dehydrated and don’t need any extra moisture in the air.

Tarantulas can also lose a generous amount of this stored water and still function.

Of course, we don’t want our tarantulas to just function, we want them to be comfortable and happy too, and that’s why I’m not sure their ability to survive without water should be used as a reason to not give them adequate access to water or not meet their humidity needs.

Tarantulas can’t absorb water through their skin

As you know tarantulas have body armor called an exoskeleton. The outer layer of the exoskeleton is called the epicuticle and contains a wax-like substance that prevents the tarantula from losing water through its body wall.

But, it also prevents Ts from getting wet easily. This may mean that tarantulas are ‘humidity-proof’ and can’t absorb moisture from the air that will aid with their hydration levels.

On the other hand, the layer of wax is different from species to species. Desert-dwelling Ts will have a thicker wax-like substance over their bodies to retain as much water as possible.

Considering this, it is likely that specific species do have the ability to absorb moisture through their skins, even with the wax layer.

Okay, some tarantula hobbyists want you to dump your humidity gauges in the trash, limit the misting to your plants and stop worrying about humidity completely.

I suppose you can go that route, but does the fact that tarantulas can survive in dry-ish environments mean that they should? Especially if they originate from humid areas?

Listen, I don’t want you to stress and obsess about keeping humidity at optimal levels all the time. That is impossible. But setting up an environment for your pet tarantula that meets its needs as closely as possible is not too much to ask.

After all, you decided to get yourself a hairy eight-legged cutie as a pet, so you better take care of it the best you can, right?

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